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Sega Master System 1 - Jailbreak
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31-05-2025 05:42PM#1
Ok, hyperbolic title aside, it's a common observation that despite outputting native RGB, the Sega Master System 1 has a very obvious jailbar effect on its output. It's just inherent to the Sony CXA chip that processes the signals, so there's no quick & easy way to fix it. There is though, the option of fitting an RGB bypass board to the console, bypassing the Sony CXA chip altogether, and using something that processes the signals in an improved fashion….so let's do that!
^^ The console in question, the Model 1 Sega Master System. Love the styling, so very 80's. It's obviously the better version of the Master System, complete with card reader (though I do have more of a nostalgic connection to the Model 2, as that's the one I owned back in the day.)
^^ A quick power up check to ensure I'm dealing with a working machine. It powers up to a green light…
^^ I don't know if it'll come through in an embedded image, but the vertical jailbars are very significant.
^^ Same again here, and there's a wavy/oscillating pattern that's static in the lines on this level.
^^ Again here, just incase they're hard to spot (not sure how they'll look until I post the thread.)
^^ Ok, console open, the patient on the table for surgery.
^^ Heatsink removed, and mainboard now sitting free.
^^ RF Modulator removal, this gives us a nice area to affix the bypass board into, and obviously RF isn't ever getting used these days.
^^ I figured while I'm in here, I'd remove all the original capacitors (they may be in spec, but they're nigh on 40 years old at this point, so a fresh set will keep things running happy for another good few years!)
^^ All capacitors now replaced with Panasonic & Rubycon's of equivalent values.
^^ Another quick test after replacing the caps, just to ensure everything is as it should be. The system powers up, the built-in game boots, and it all looks good.
^^ First thing is first, we need to sever the RGB & Sync lines going to the Multi-Out. These lines are now redundant, as we will be feeding the newer, better handled signals to the multi-out ourselves. The above shows where I cut the traces for two of the RGB signals (can't remember which two.) This mainboard version has the traces on the top side of the board, instead of the bottom as shown in many tutorials, so this way is a little more delicate.
^^ The other signal of the three RGB lines now cut too.
*** I forgot to show cutting the trace for the Sync line on the underside of the board.***
^^ This is the RGB Bypass I'll be using. I bought the version on OSH Park, which I'll keep as a reference, but with some blippidy blops I was able to adapt the files to have my own printed by PCBway (hence the blue and not the purple of OSH Park.) It's a matter of adding on the 7314 video chip, some caps, some resistors, and that's it.
^^ It's designed to mount in where the RF Modulator was. I lay down a bit of kapton tape as an insulator, but the bottom of the bypass doesn't look like it's a risk anyway.
^^ I solder three resistor legs into the ground anchors for the RF Modulator….
^^ And the designer of the PCB has lined up the anchor points so the resistor legs solder directly to them….it's rock solid like this. I've also removed the three SMD capacitors as the cable I'm using has the capacitors inside the cable, so the ones here aren't needed. So instead of using the RGB Outputs, you simply use the capacitor input pads as the video outputs.
^^ 5v fed into the bypass board from the modulator power point, and the three RGB lines are tapped off the board and fed into the RGB inputs on the bypass too.
^^ Sync now fed to the board. The RGB output lines are now in place and fed directly to the multi-out as per the tutorials (though the scart cable I'm using is wired for sync off a different pin on the multi-out, so I changed the white wire to that point later on.)
^^ All wired up, and ready to test…
^^ Hmm, it's looking very sharp…no jailbars in the whites of the Sega logo anyway…
^^ Aw man….the image is SSOOOO much better. The colours are so punchy in person, the image is super sharp, and very importantly, the jailbars are all but gone!
^^ That ugly oscillating pattern is gone too….it looks great.
^^ Reassembly time, I clean off the heatsink contact area, and put some fresh MX-2 in place, so the heatsink should transfer heat into the heatsink more efficiently now.
^^ Job done.
^^ Beauty shot to close 😎
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